Switch construction



June 1942- Q N. c. SCHELLENGER 2,286,162

SWITCH CONSTRUCTION Filed 001;. 20, 1939 2 Sheets-Sheet l msmzw Nam/T527E. fiche/Linger '33. gww ()3, Mm; i

Jun; 9, 1942.

N. C. SCHELLENGER SWITCH CONSTRUCTION Filed 00%. 20, 1939 2 Sheets-Sheet2 f Heal/21y 5121/52 ZaZEd Nam 727T? C. fiche/[527 Patented June 9, 1942swrrcn CONSTRUCTION Newton 0. Schellenger, El Paso, Tex., assignor toChicago Telephone Supply Company, Elkhart, Ind., a corporation ofIndiana Application October 20, 1939, Serial No. 300,321

9 Claims.

This invention relates to electric snap switches; and like the,copending application of Newton C. Schellenger, Serial No. 83,963,filed June 6, 1936, now Patent No. 2,177,284, of which this applicationis a continuation in part, refers particularly to snap switches of thetype used in radio receivers.

From the standpoint of compactness and mechanical design, the switchconstruction illustrated in the aforesaid copending application hasproved to be exceptionally satisfactory. Briefly, this switch structureconsists of a fiat base of insulating material from which two spacedstationary contacts and a pivot post project, the contacts beingelectrically bridged to close the switch .by a movable contactor whichis slid across the surface of the base in an arcuate path by aninsulated carrier pivoted to the post.

The carrier overlies the contactor and is connected thereto by tangs orlugs struck up from the contactor and received in apertures in thecarrier. The maintenance of this driving connection depends upon thecarrier being constrained against movement away from the base beyond apredetermined extent, as the tangs or lugs merely project into theapertures of the carrier.

When the switch is assembled, the carrier is yieldingly restrainedagainst movement away from the base by the toggle spring which is soconnected between the carrier and the actuating cam as to have adownward force component acting to hold the carrier against thecontactor.

It has been found, however, that in some instances, where the switch ishandled quite roughly during its installation, the carrier sometimesjumps away from the base sufilciently to permit its being disengagedfrom the movable contacts. The most frequent source of this trouble hasbeen traced to sharp blows, as by a light hammer, applied on the end ofthe volume control shaft.

While reformation or strengthening of the spring to impose a greaterdownward thrust onto the contactor carrier would minimize thisobjection, it would do so only at the expense of smoothness and ease ofswitch operation; for any increase in spring tension would entailgreater friction.

This invention, therefore, has, as one of its objects. shoulder orabutment carried by the switch casing or some other stationary part andoverlying the contactor carrier to definitely limit movement thereofaway from the base and thus insure the the provision of a simplelimitingmaintenance of the driving connection between carrier andcontactor.

The connected contactor and carrier swing in an are about a fixed pivotaxis; and the stationary contacts are so positioned as to besubstantially on a line radial to this axis. Consequently, one contactis closer to the pivot axis than the other.

This disposition of the stationary contacts with relation to the arcuatepath of the bridging contactor results in a slower break between theinner stationary contact, that is, the one nearest the pivot axis, andthe bridging contactor than at the outer stationary contact; and wherethe movable bridging contactor is a resilient U-shaped band with theends thereof providing its contact engaging surfaces, there is also lessrelative wiping action between the inner stationary contact and itscooperating leg of the movable contactor than between the outerstationary contact and its cooperating leg of the movable contactor.

As a result of this inequality in the velocity of the break and wipingaction, at the two stationary contacts, the arcing load is carriedprimarily at the inner contact, thus accelerating the destructiveeffects of the arc and materially shortening the life of the switch.

To overcome this objection, the present invention has, as another of itsobjects, to so guide the motion of the movable bridging contactor astoinsure its engaging the inner stationary contact first, during closureof the switch, and

disengaging the inner contact last, during openv ing of the switch. Inthis manner, it is possible to balance the ratio of arcing at the innerand outer contacts against the cleaning action resulting from wipingengagement between the contacts and contactor so that an eflectequivalent to that which would be obtained if the two stationarycontacts were equidistant from the pivot axis, is

achieved.

Another object of this invention, directed to the longevity of theswitch, resides in the proing away from the stationary contacts duringclosure of the switch.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed, and more particularly the invention constructed imaccordancewith the best modes so far devised for the practical application of theprinciples thereof, and in which- Figure 1 is a longitudinal sectionalview through a switch constructed in accordance with this invention andillustrating the same mountedon the back of a volume control;

Figure 2 is a cross sectional view taken through Figure 1 on the planeof the line 2--2 and showing the switch open;

Figure 3 is a view similar to Figure 2 but showing the switch closed;

Figures 4 and 5 are detail fragmentary views similar to part of Figure 1and illustrating a slightly modified manner of holding the contactorcarrier in place;

Figure 6 is a detail sectional view taken through Figure 2 on the planeof the line 66; and

Figures '7, 8 and 9 are diagrammatic views to illustrate progressivelythe manner in which the bridging contactor engages the stationarycontacts during closure of the switch.

Referring now particularly to the accompanying drawings, in which likenumerals indicate like parts, the numeral 5 designates the base of theswitch which, as is customary, comprises a circular disc of suitableinsulating material and closes one end of a cylindrical metal shell 6.The base and the shell thus constitute a substantially cup-shaped switchhousing.

Fixed to the base and projecting from the inner fiat surface thereof isa pivot post I. This post is located near the edge of the base and hasan annular enlargement or flange 8 located medially of its ends.

Also fixed to the base and-projecting up from its inner surface are twospaced stationary contacts 9 and I0. These two contacts are on a linesubstantially radial to the axis of the pivot post, so that one (thecontact 9) is located substantially medially between the pivot post andthe other contact. Terminals II and I2 mounted on the outer face of thebase and connected respectively to the contacts 9 and I0 provide forconnecting the switch in the circuit to be controlled.

Closure of the switch is efiected by engaging a bridging contactor l3with the two stationary contacts. This bridging contactor consists of aterial with a hole in its apexby which it is hooked onto the pivot post,the hole being large enough to permit the flange 8 to pass therethroughso that the carrier may be disposed between the flange and the base. Inthis position, the carrier overlies the stationary contacts and thebridging contactor.

The connection between the carrier and the bridging contactor consistsof a lug or tang l6 extending from one edge of the closed end of the Uand pivotally received in a hole I! in the carrier and two similar lugor tangs [8 extending up from the end portions of the legs of the U tobe received in an enlarged opening l9. The width of the opening [9 isslightly less than the distance across the outermost corners of thetangs or lugs l8 when the U-shaped contactor is free so that the legs ofthe U are held under a slight spring tension for a purpose to behereinafter described.

It will be apparent that this manner of drivingly connecting thebridging contactor with the carrier permits ready disassembly of theseparts by movement of the carrier away from the base. Such bodilymovement of the carrier is opposed by the downward force component of atoggle spring 20 which is connected between the carrier and an actuatingcam 2| pivotally mounted on the post.-

As described in the aforesaid copending appli-' cation, the spring 20snaps the contactor carrier from one position to the other as theactuating cam is moved from one limit of motion to the other; and byvirtue of the fact that the point of connection between the spring andthe actuating cam is above the connection of the spring to the contactorcarrier, a downward thrust is imposed upon the carrier to maintain thesame properly assembled with the contactor.

Ordinarily, this downward thrust of the spring is suflicient to keepthese parts properly assembled, but in some instances, during theassembly of the switch in the radio chassis or other device with whichit is used, the handling to which the switch is subjected may cause thecontactor carrier to jump away from the base sufficiently to permit itsdisengagement from the bridging contactor.

This condition is particularly prevalent where the switch is mounted onthe back of a volume control 22, as shown in Figure 1; and for somereason or other, a light blow is struck on the end of the control shaft23 during assembly of the unit in the chassis or other device with whichit is used.

To guard against this objectionable possibility, a tongue 24 is struckfrom the side wall or shell 6 to overlie the. contactor carrier, asclearly shown in Figures 1, 2 and 3.

substantially U-shaped band of resilient metal having its free endportions l4 directed angularly toward each other to define an acuteangle so as to engage the cylindrical surfaces of the stationarycontacts with a wedging action.

The movable bridging contactor is slid across the surface of the base toand from bridging engagement with the stationary contacts by aninsulated carrier l5 to which the bridging contactor is connected in amanner to be hereinafter described.

The carrier preferably consists of a substantially segment-shaped pieceof flat insulating ma- It is preferable to strike this tongue 24 fromthe wall of an indentation 25 in the shell. This permits the use of arelatively short tongue and provides a uniform overhang over theadjacent edge of the carrier which is arcuate and concentric to thepivot axis.

The location of this tongue, as best shown in Figure 1, so limits themovement of the carrier away from the base as to preclude disengage mentof its driving connection with the bridging contactor.

While it is preferable to provide this tongue. 24 in the mannerdescribed, it is possible, of course, to have it struck from the rim oredge of the metal side wall or shell, as shown at 26 in Figure 4; or itmight be struck down from the end wall 21 of the volume control housingas at 28 in Figure 5.

The mechanism of the volume control forms no part of this invention and,therefore, need not be described. It is sufiicient to note that rotationof the shaft 23 carrie a driver 29 along an arcuate path to transientlyengage the actuating cam so that the switch may be opened and closed byrotation of the shaft 23.

In switches of this type heretofore in use, no provision was made toguard against the inevitable inequality in the amount of arcing andwiping action at the two stationary contacts.

The present invention, however, provides a construction by which theratio of arcing at the contacts may be so balanced against the cleaningefiect obtained by the wiping action, that the result is substantiallythe same as though both stationary contacts were equidistant from thepivot axis. This desideratum is achieved by con-- straining the arcuatemotion of the bridging contactor to a defined path having a definiterelationship to the positions of the stationary contacts; and it is forthis purpose that the tangs or lugs l8 are held in engagement with theside edges of the opening l9 under spring tension.

As best shown in Figures '7, 8 and 9, the motion of the movable bridgingcontactor with relation to the stationary contacts during closure of theswitch is such that engagement is first established between the innercontact 9 and its cooperating leg of the bridging contactor; andthereafter, as switch closure progresses, the engaged inner leg of thebridging contactor moves inwardly against the prevailing spring tensionwhich should be approximately one to one and one-half ounces,

to disengage its tank or lug from the edge of the opening.

Continued closure next effects engagement of r the outer leg of thebridging contactor with the outer stationary contact and when thisoccurs, both legs of the bridging contactor are free from the guidingaction of the hole l9 so that the bridging contactor is free to pivot asrequired to equalize the pressure on the two contacts.

Hence, it will be observed that the actual closure of the switch takesplace at the outer contact.

In opening, the reverse order obtains, that is, the outer contact isfirst disengaged by the contactor. This draws an appreciable arc. Then,while this are continues, the inner contact is disengaged by thecontactor accompanied b a slight arc. The destructive efiect of thearcing is thus greatest at the outer contact; but inasmuch as the outerleg of the bridging contactor not only has greater kinetic energy thanthe inner leg thereof but also moves farther than the inner leg, it willbe seen that the inequality of the arcing at the inner and outercontacts isoflset by the greater cleaning action available at the outercontact.

The desirable balance between the ratio of arcing and cleaning action isthus effected with a result, as noted hereinbefore, that the switchaction is similar to that which would be obtained greater thanapproximately forty-five (45) degrees, the bridging contactor bouncesduring closure of the switch, drawing small but objectionable arcs.

It is, thus, preferable to maintain this angle substantially mediallybetween twenty-six (26) and forty-five (45) degrees.

Heretofore, it has been customary to use copper for the staionarycontacts and phosphor bronze for the bridging contactor when theU-shaped construction is employed and copper when a solid constructionis employed, as in the aforesaid copending application. I

In all instances, the contacts were quite heavily plated with silver sothat the actual switching was done between silver to silver. Thisarrangement, while substantially satisfactory, has been found o be farexcelled if one of the cooperating contacts, or at least its contactengaging surface, is brass and the other remains silver.

In the construction illustrated and described wherein the bridgingcontactor is a U-shaped resilient band, it is preferable to make'thecontactor of spring brass and to have the stationary contacts formed ofcopperheavily silver plated.

The exact reason for the greatly improved re sults obtained by thiscombination of metals has not been definitely determined; but the answeris easily over the silver plated stationary contacts.

In life tests conducted with switches identical in mechanical design andconstruction except that in one instance, phosphor bronze bridgingcontactors were employed and in the other, spring brass bridgingcontactors were used, it was found that contact resistance in the formerran as high as thirty thousandths (.030) of an ohm after only fivethousand (5,000) cycles of opera tionand as high as sixty-sixthousandths (.066) of an ohm at twenty-five thousand (25,000) cycles;whereas, in the latter case, the contact resistance during twenty-fivethousand (25,000) cycles never rose above approximately seventhousandths (.007) of an ohm, and only after thirty-two thousand(32,000) cycles of operation did the contact resistance rise above tenthousandths (.010) of an ohm.

This remarkable difference in contact resistance was wholly unexpectedand as unpredictable as it now appears to be inexplicable.

Because brass is susceptible to rather rapid corrosion in certainambient atmospheric conditions; and as many plants employ corrosivegases in their manufacturing processes, it is desirable to protect thebrass bridging contactor against such corrosive effects. To this end, avery light silver plating is applied thereto. This plating protects thecontactor against corrosion but does not affect the functioning of theswitch or in anywise increase contact resistance, as it wears oil at itscontact engaging portions during the first few operations of the switchso that thereafter the desirable effect of plain brass against silver isobtained.

While silver plating as a protection against corrosive atmospheres isgenerally satisfactory,

other metals may be employed for this protective plating where theswitch is to be used in loca tions subject to fumes or gaseousatmospheres a substantial improvement in snap switches of the typedescribed, for it obviates the possibility herent in this design;further lengthens the useful life of the switch by keeping the contactresistance low through the use of a brass contactor engaging silvercontacts; and by so constructing the movable bridging contactor that itwill not stick in closed position nor bounce during closure.

What I claim as my invention is:

g 1. In a snap switch for closing and opening an electrical circuit: amovable contact assembly constrained to oscillatory motion about a'fixedaxis and comprising a carrier, a bridging contactor having yieldablecontact engaging portions and a connection between the carrier and thecontactor held tight by spring tension as long as the yieldable contactengaging portions of the contactor are free so that the contactor andits carrier are movable as a unit without relative motion therebetween;and a pair of spaced stationary contacts arranged on a linesubstantially radial to said fixed axis so that one contact is closer tothe axis than the other, said contacts being so positioned with relationto the arcuate motion of the movable bridging contactor that duringswitch closure engagement is first effected between the stationarycontact nearest the pivot axis and its cooperating portion of thebridging contactor and in opening disengagement is last effected betweensaid inner contact and its cooperating portion of the bridgingcontactor, so that closure and opening of the electrical circuitcontrolled by the switch takes place between the stationary contactfarthest from said fixed axis and its respective contact engagingportion of the contactor which moves faster and farther than the othercontact engaging portion.

2. In an electric switch for closing and opening an electrical circuit:an insulating base; a contactor carrier; a pivotal connection betweenthe carrier and the base constraining the carrier to an arcuate motionacross the base and radial to the axis of the connection; a pair ofspaced stationary contacts carried by the base and so positioned thatone is closer to said pivot axis than the other; a substantiallyU-shaped resilient bridging contactor between the base and the carrierand having contact engaging portions at its outer free ends engageablewith the stationary contacts; and a driving connection between thecarrier and said U-shaped bridging contactor, said connection utilizingthe resilience of the bridging contactor to hold the contactor againstany motion with respect to the carrier as long as the switch is open andin such definite relationship to-the stationary contacts that duringswitch closure engagement is first established between the bridgingcontactor and the stationary contact nearest the pivot axis, and inopening of the switch disengagement isfirst effected between thebridging contactor and the stationary contact farthest from the pivotaxis, so that closure and opening of the electrical circuit controlledby the switch takes place between the stationary contact farthest fromsaid fixed. axis and its I respective contact engaging portion of thecontactor which moves faster and farther and thus has greater wipingaction than the other contact engaging portion.

3. In an electric switch of the character described: a fiat insulatingbase; two spaced stationary contacts carried by the base and extendingup from the face thereof; a contactor carrier movable across said faceof the base; a pivotal connection between the carrier and the base constraining the carrier to motion in an arc radial toa fixed axis closerto one of said stationary contacts than the other; a substantiallyU-shaped resilient bridging contactor between the carrier and the basewith its free ends facing the stationary contacts to be engageabletherewith and thereby close the electrical circuit controlled by theswitch; and a driving connection between the bridging contactor and saidcarrier comprising. a lug near the closed end of the U and engagingin ahole in the carrier; and lugs near the free ends of the U held inengagement with shoulders on the carrier by the normal resilience of thebridging contactor as long as the switch is open so that the contactormoves directly with the carrier in a definite position with relation tothe carrier and in a defined path, and said stationary contacts being sopositioned with relation to said defined path of the bridging contactorthat during closure of the switch engagement is first establishedbetween the stationary contact nearest to said fixed axis and its leg ofthe bridging contactor, and in opening of the switch disengagement isfirst effected between the stationary contact farthest from the saidfixed axis and its leg of the bridging contact, so that closure andopening of the electrical circuit controlled by the switch takes placebetween the stationary contact farthest from said fixed axis and itsrespective contact engaging portion of the contactor which moves fasterand farther thus has greater wiping action.

4. In an electric switch: an insulating base having a fiat face;stationary contacts carried by the base and exposed at said fiat face; amovable bridging contactor slidable across the fiat face of the base toand from engagement with the stationary contacts; a carrier for themovable contactor overlying the same; a driving connection between thecarrier and movable contactor readily disengageable by movement of thecarrier away from the base; a snap actuating mechanism for the carrierincluding a spring so connected with the carrier as to yieldingly urgethe carrier toward the base to normally hold the carrier assembled withthe bridging contactor; and a fixed abutment overlying the carrier topositively limit movement of the carrier .away from the base a distanceinsufficient to enable disengagement of the driving connection betweenthe carrier and the bridging contactor.

5. In an electric switch: a flat substantially circular base; a metalside wall encircling the periphery of the base and cooperating therewithto form a substantially cup-shaped switch housing; spaced stationarycontacts carried by the bees and exposed on its inner face; a movablebridging contactor slidable across the inner face of the base to andfrom engagement with the stationary contacts; a carrier for the bridgingcontactor overlying the inner face of the base and having the bridgingcontactor confined between it and the base; a driving connection betweenthe carrier and bridging contactor readily disengageable by movement ofthe carrier away form the base; a pivotal connection between the carrierand the base constraining the carrier and dial to a fixed pivot, saidcarrier having an armateouter edge concentric to the pivot axis; andaperiphery of the base and cooperating therewith to form a substantiallycup-shaped switch housing;'spaced stationary contacts carried by thebase and exposed on its inner face; a movable bridging contactorslidable across the inner face of the base to and from engagement withthe stationary contacts; a carrier for the bridging contactor'overlyingthe inner face of the base and having the bridging contactor confinedbetween it and the base; a driving connection between the carrier andbridging contactor readily disengageable by movement of the carrier awayfrom the base; a pivotalconnection between the carrier and the baseconstraining the carrier and the bridging contactor to an arcuate motionradial to a fixed pivot, said carrier having an arcuate outer edgeconcentric to the pivot axis; an

of the contactor to yield as they engage their respective stationarycontacts.

8. In an electric snap switch: an insulating base; a pair of spacedstationary contacts on the base andprojecting up from the base toprovide contact surfaces substantially perpendicular to the base; abridging contactor comprising 'a resilient U-shaped band having its freeend portions directed toward each other to provide the sides of a wedgeengageable between the stationary contacts; a contactor carrieroverlying the base and confining the contactor between it and the base;and means connecting the contactor with the carrier comprising a lug onthe closed end of the contactor loosely en-' gaging in a hole in thecarrier, and lugs on the free end portions of the contactor held inengagement with the opposite sides of a hole in the carrier bytheresiliency of the contactor so that the contactor is at all times underan initial spring tension and is held in a definite fixed position withrelation to the carrier.

9. In an electric snap switch: a pair of spaced stationary contacts; amovable bridging contactor comprising a U-shaped resilient band, the

. free ends of which provide its contact engaging indentation in themetal side wall having its bottom surface close to the concentric edgeof the carrier; and a lug extending from the bottom wall of saidindentation to overly the concentric edge of the carrier to limitmovement of the carrier away from the base and preclude disengagement ofthe driving connection between the carrier and bridging contactor.

7. In an electric snap switch: an insulating base; a pair of spacedstationary contacts on the base; a bridging contactor movable across thebase to and from a position electrically bridging the contacts, saidcontactor comprising a resilient U-shaped band the free ends of whichprovide the contact portions engageable with the stationary contacts; acontactor carrier for moving the contactor to and from bridgingposition;

and means for connecting the contactor with the carrier comprising aloose pivotal connection between the closed end of the U-shapedcontactor and the carrier and abutments on the free ends of thecontactor engaging spaced shoulders on the carrier, said shoulders beingspaced apart a distance such that the resiliency of the contactor holdsthe abutments on the free ends of the contactor resiliently inengagement with the shoulders so that the contactor is at all timesunder an initial spring tension and retains a predetermined fixedposition with relation to the carrier while allowing the free endsportions; means constraining the contact engaging portions to motionalong radially spaced inner and outer arcs during travel of thecontactor to and from switch, closing position and as long as thecontactor is disengaged from the stationary contacts, while enablingsaid contact engaging portions to be sprung in consequence to engagementwith their respective stationary contacts, both of said arcs beingconcentric to a fixed axis, and said constraining means so holding thecontact engaging portions that deflection of one .by engagement with itsrespective stationary contact does not shift the other from its definedarcuate path, one of said stationary contacts being in the path of eachof said contact engaging portions and said stationary contacts being solocated with relation to the contact engaging portions that a linepassing through the points on the stationary contacts initially engagedby the contact engaging porcontact engaging tions intersects a linepassing through the points on the contact engaging portions whichinitially engage the contacts, at a point lying between the fixed axisand the outer arc, so that closure and opening of an electric circuitcontrolled by the switch at all times occurs between the outer portionand its respective stationary contact. Q

NEWTON C. SCHELLENGER.

